1. Field of the Invention
The present invention relates to a liquid crystal display having a plastic substrate.
2. Description of the Related Art:
A plastic substrate is expected to be useful as a substrate for a liquid crystal display because of the following characteristics: It is thin, light, flexible and is difficult to break; it has satisfactory workability; and it is possible to form an element with a large surface area thereon. A conventional glass substrate does not have such characteristics.
Known liquid crystal displays having a plastic substrate are disclosed in Japanese Laid-Open Patent Publication Nos. 59-204545, 60-260019 and 55-114563.
The liquid crystal display disclosed in Japanese Laid-Open Patent Publication No. 55-114563 comprises a pair of plastic substrates 103 and a liquid crystal 110 sandwiched therebetween as is shown in FIG. 3. On the inner opposing surface of each of the plastic substrates 103 are successively formed an anchor agent layer 104, an undercoat layer 105 and a transparent electrode 106. On the outer surface of each of the plastic substrates 103 is formed another anchor agent layer 102. The plastic substrates 103 are sealed with a pair of sealing materials 109. The production method for such a liquid crystal display is as follows:
The plastic substrate 103 is dipped in a solution including an anchor agent such as amino silane and epoxy silane and dried to form the anchor agent layers 102 and 104 on its both surfaces. On the anchor agent layer 104, the undercoat layer 105 made from silicon oxide, etc. and the transparent electrode 106 are successively formed by sputtering, etc. Then, the plastic substrates 103 are set opposing each other, having the surfaces bearing the transparent electrodes 106, etc. facing each other, so as to sandwich the liquid crystal 110 therebetween by a known method. The opposing plastic substrates 103 are sealed with the sealing materials 109.
The anchor agent layer 104 is formed between the plastic substrate 103 and the undercoat layer 105 in order to improve adhesiveness therebetween. However, the plastic substrate 103 can be distorted by itself or due to a difference in the coefficients of the thermal expansion of the plastic substrate 103 and the undercoat layer 105. This distortion causes peeling between the plastic substrate 103 and the undercoat layer 105 or cracks in the undercoat layer 105 and the transparent electrode 106. These disadvantages are fatal to a liquid crystal display.
A use of a hard coat layer made from an organic resin such as organosilane resins, acrylic resins, melamine resins and urethane resins instead of the anchor agent layer 104 has been considered. In this case, however, the above-mentioned problems of peeling and cracks still remain.